With the proliferation of wireless communication and mobile radio stations, the base station(s) (BS) for such systems can be located in more populated and public areas, such as city centers. As such, the industrial and aesthetic design aspects of such base stations, including the enclosure for the antenna structures, becomes a more important feature.
A radome is generally understood to be a weatherproof enclosure for an antenna system. As is generally understood, the radome houses the antenna assembly and structure for the base station of the mobile radio system. One common configuration of a radome is a generally round or spherical shape. However, with the different designs and requirements for antennas and the radomes for such antennas, there are requirements for flat surfaces or front faces, rather than the more common spherical design.
The material for a radome is generally plastic, to provide communication transparency for antenna signals. The backside of the base station antenna structure, also referred to as a heatsink, is generally manufactured from a thermally conductive material, such as die cast aluminum. The heatsink will include cooling ribs, which are used for passive cooling of the antenna heat generating elements.
The radome is typically coupled to the heatsink in a secure manner. Normally, the radome is coupled to the heatsink using fixation devices and fasteners such as screws. There is also normally a water proof gasket between the radome and the heatsink. When the radome is fixed to the heatsink, the structure is generally stiff or rigid.
The plastic radome and aluminum heatsink parts or components for a base station antenna are typically designed so that in a normal or ambient temperature environment, the different parts fit together in a reliable and secure manner. However, plastic and aluminum parts typically have different thermal expansion characteristics. Thus, when the temperature of the environment in which the base station antenna system is located changes, there can be expansion and contraction of the plastic and aluminum parts. Due to the different thermal expansion characteristics of the plastic and aluminum parts, these parts can expand and contract differently. This can result in problems with the fit of the different parts as well as the integrity of the radome structure.
Referring to FIGS. 1A and 1B, one phenomenon that can occur when there are temperature changes, is what is referred to as a “swelling” of the different materials. As shown in FIG. 1A, the radome 10 and the heatsink 20 are fixed together by fixing points 12, which can be screws. A gasket 14 is provided between the radome 10 and heatsink 20. FIG. 1A illustrates the radome and heatsink structure in a normal or ambient temperature environment.
In the example of FIG. 1B, there has been a temperature change. In this case, the temperature has risen resulting in expansion of the different radome 10 and the heatsink 20. However, since the plastic radome 10 expands faster or to a greater degree than the aluminum heatsink 20, the originally flat surface shape of the plastic radome 10 takes on a “curved” or rounded shape or form.
A change in the shape of the radome can be undesirable. The radiation from antenna elements will be impacted if the distance from the antenna element to the radome changes. Also, if the radome develops a curved shape, this can be noticeable when the original shape of the radome was planar or flat.
Also, the different degrees of expansion can also result in structural problems. The bending of the plastic radome relative to the aluminum heatsink can place stresses on the various parts including the fixation points. These stresses can affect the integrity of the radome structure as well as the waterproofness of the structure. It would be advantageous to provide a mechanical structure for base station antenna enclosure that accommodates thermal expansion while maintaining a shape, waterproofness and aesthetic design considerations of the radome.
Accordingly, it would be desirable to provide an antenna housing structure that addresses at least some of the problems identified above.